Portable lighting used in wet or conductive locations must be operated at no more than ____volts D.C., or must be protected by GFCI's.

The correct answer is 12 volts D.C. because operating portable lighting at this voltage level ensures a significant reduction in the risk of electric shock when used in wet or conductive locations. This is especially critical in environments where water or other conductive materials can increase the likelihood of electric current traveling through unintended paths, posing serious safety hazards.

By limiting the voltage to 12 volts D.C., the electrical energy available is lower, making it less capable of causing harm if a person were to come into contact with the light or its wiring. Additionally, using Ground Fault Circuit Interrupters (GFCIs) provides an extra layer of protection by monitoring electrical flow and quickly cutting off the power supply in case of a fault, which further enhances safety in these environments.

Choosing a voltage higher than 12 volts can increase the potential for severe electric shock or electrocution, especially in wet conditions. Therefore, the regulation emphasizes 12 volts D.C. to maintain a safe working environment for individuals in potentially hazardous areas.